Support Rack response bodies that allow to_ary (#22)

Newer Rack versions support bodies that respond to `to_ary` and in newer versions of Rails the Rails response body does as well. It seems previously we would not treat such response bodies correctly, meaning they would not get cached by Idempo (providing locking but no caching). This should be rectified with this PR - when running on Rack 3 (and newer Rails) `to_ary` will be called on the body, materializing it into an Array of Strings.

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         ruby:
-          - '2.7'
+          - "2.7"
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -37,11 +37,16 @@ jobs:
     name: Specs
     runs-on: ubuntu-22.04
     if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
+    env:
+      IDEMPO_RACK_VERSION: ${{ matrix.rack }}
     strategy:
       matrix:
         ruby:
-          - '2.7'
-          - '3.2'
+          - "2.7"
+          - "3.2"
+        rack:
+          - "2.0"
+          - "3.0"
     services:
       mysql:
         image: mysql:5.7
@@ -65,6 +70,7 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1
         with:

idempo.gemspec

@@ -36,7 +36,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   # Uncomment to register a new dependency of your gem
-  spec.add_dependency "rack"
+  spec.add_dependency "rack", "~> #{ENV.fetch("IDEMPO_RACK_VERSION", "3.0")}"
   spec.add_dependency "msgpack"
   spec.add_dependency "measurometer", "~> 1.3"
 

lib/idempo.rb

@@ -7,6 +7,7 @@
 require "msgpack"
 require "zlib"
 require "set"
+require "rack"
 
 require "idempo/version"
 
@@ -57,6 +58,12 @@ def call(env)
       status, headers, body = @app.call(env)
 
       expires_in_seconds = (headers.delete("X-Idempo-Persist-For-Seconds") || @persist_for_seconds).to_i
+
+      # In some cases `body` could respond to to_ary. In this case, we don't need to call .close on body afterwards.
+      #
+      # @see https://github.com/rack/rack/blob/main/SPEC.rdoc#the-body-
+      body = body.to_ary if rack_v3? && body.respond_to?(:to_ary)
+
       if response_may_be_persisted?(status, headers, body)
         # Body is replaced with a cached version since a Rack response body is not rewindable
         marshaled_response, body = serialize_response(status, headers, body)
@@ -76,6 +83,10 @@ def call(env)
 
   private
 
+  def rack_v3?
+    Gem::Version.new(Rack.release) >= Gem::Version.new("3.0")
+  end
+
   def from_persisted_response(marshaled_response)
     if marshaled_response[-2..] != ":1"
       raise Error, "Unknown serialization of the marshaled response"
@@ -104,6 +115,7 @@ def serialize_response(status, headers, rack_response_body)
     # does not
     [deflated_message_packed_str, body_chunks]
   ensure
+    # This will not be applied to response bodies of Array type.
     rack_response_body.close if rack_response_body.respond_to?(:close)
   end
 

spec/idempo_spec.rb

@@ -60,7 +60,7 @@
   describe "when no double requests are in progress" do
     let(:app) do
       the_app = ->(env) {
-        [200, {"X-Foo" => "bar"}, [Random.new.bytes(15), env["rack.input"].read]]
+        [200, {"X-Foo" => "bar"}, [Random.new.bytes(15), env["rack.input"]&.read]]
       }
       Idempo.new(the_app, backend: Idempo::MemoryBackend.new)
     end